Pegatron India was sparked by a short-circuit after an electrical switch was left on, following testing of the devices as they were being put together, two sources briefed on the matter told Reuters.
The lapse at key Apple supplier Pegatron's only factory in India, located in the southern state of Tamil Nadu, cost two straight days of lost production.
After Reuters sent queries to Pegatron for this report, the firm told the Taiwan stock exchange on Wednesday that «a small switchboard experienced an accident» at the factory on Sunday.
A spokesperson late on Wednesday said production had restarted, without providing further details.
In a statement on Monday, Pegatron said there were no injuries in the fire, which it described as a «spark incident» whose cause would be determined, while adding that it did not have significant impact on finances and operations.
Apple did not respond to a request for comment and has not yet commented on the matter. Its representatives have been in touch with Pegatron after the incident, Reuters has reported.
A senior Tamil Nadu government source, and another industry source briefed on the matter, detailed how Sunday's events unfolded. Both spoke on condition of anonymity as the matter is sensitive.
After putting together about 70 iPhone parts, workers at the Pegatron plant usually charge the device batteries up to a level of 50%